This invention relates to a transfer system for a power-and-free conveyor.
Throughout the specification and the appended claims, the terms "front" or "forward" and "rear" or "rearward" are based on the direction of travel of the conveyor. Thus, the former refers to the direction in which the conveyor advances and the latter to the opposite direction.
With power-and-free conveyors, the drive force of power trolleys is transmitted to free trolleys through pushers. These conveyors have a distinct feature that free trolleys can be transferred as desired from a first free rail, serving as the main track, to a second free rail branching off from the first free rail. Such conveyors are useful and essential to the automation of quantity flow production. For example, several kinds of products from different processes may be transported on a conveyor and then fed to specified work lines on automatic selection. Articles which require a special operation such as readjustment may be transferred onto a branch line so that the articles can be worked on independently of the flow on the main line. The conveyor system may include an accumulation line for the adjustment of the rate or frequency of operation or a number of elongated branch lines serving as a storage for storing articles as sorted out.
At the branching portion of conveyor systems, the carrier disengaged from a pusher on the drive chain of the first power rail must be engaged by a pusher on the drive chain of the second power rail after traveling along the branch rail. At the section between the position where the carrier is disengaged from one pusher and the position where it is engaged by the other pusher, the carrier needs to be propelled by some auxiliary means. For this purpose, the carrier is usually provided on its rear free trolley with an auxiliary dog adapted to be engaged by a pusher on the power rail which is positioned at a reduced spacing from the free rail in the above-mentioned section so that the pusher pushes the carrier from behind. Alternatively, the rear free trolley is equipped with an engagement body which is engaged by another pusher on the drive chain for pushing the carrier from behind. Thus, the conventional systems require auxiliary pushing means which renders the system complex and costly.